With spring comes the increased risk for severe weather around the Mahoning and Shenango valleys. After saturating rains on Tuesday caused some soggy yards and minor flooding, there is a chance of severe weather through 10 p.m. We hear the terms of severe risk categories, which fall under categories like thunderstorms: marginal, slight, enhanced, moderate, to high. But what do they mean? What is the difference being a tornado watch and a warning? Are there increased risks that come with tornadoes that come during the night? 21 News spoke with Aaron Treadway, a severe weather expert who works for the National Weather Service. He breaks down all the terms so you can be better prepared when extreme weather hits near you. Listen up to this important information.